WordPress cannot find the database driver.
WHAT IT MEANS
The PHP extension WordPress uses to talk to MySQL is not enabled.
THE FIX
cPanel > Select PHP Version > Extensions.
Enable mysqli and pdo_mysql. Save.
WHEN THIS HAPPENS
After changing PHP version. Each version has its own extension selections, and a newly selected version starts with defaults.
This is the most common cause.
After a server migration, where the new environment differs.
ON A VERY OLD SITE
WordPress removed support for the original mysql extension. A site written against it needs updating, or it will not connect on any current PHP version.
Updating WordPress and the affected plugins resolves it.
CHECKING WHAT IS ENABLED
The same Extensions screen lists everything available with its state.
AFTER ENABLING
Reload the site. No restart is required.
IF IT PERSISTS
Confirm you enabled the extension for the PHP version actually assigned to that domain, under MultiPHP Manager.
